During the pre-production design
phase, submarine Seaview went through various incarnations. One
of the original concepts documented was that of the more conventional
tear-drop shape submersible with a totally unconventional transparent
viewing room aft of the conning tower. Two
indications of this were made public. One was the original cover of the
Voyage novel published June 17th of 1961, about three weeks prior
to the film’s release July 12th.

Another
relic of pre-production artwork was included in a photo-promo
insert included in the June 7th issue of Motion Picture Exhibitor,
artwork which depicted the same transparent viewing room as
graced the cover of the novel, but from the opposite perspective —inside the
submarine.

I’d never been absolutely sure about
the factualness of this early reported design, but the two graphics
in combination, one of which (that included in the Motion Picture
Exhibitor insert) definitely came from the Twentieth Century
Fox art department, are pretty convincing evidence.